I have seen an outfit coming on site at 5.30am when staying at Cadeside. No problem as long as the warden is happy and has given prior consent then that is totally fine. I think in this case the people had come off a morning ferry somewhere

I never said you were. ID did say that you need to ask staff. I suspect that you will not be able to pay for the night that you do not attend also and that it will result in an unused booking. By all means ask.

The other thing not mentioned on the post is that the additional Sunday that he wants to pay for and not use is not the usual lower occupation Sunday. On the CMC topic he says that the Monday in question is a bank holiday Monday in May when, of course Sunday night is far more in demand

They are best advised to contact the site. Whilst if there was a genuine reason for arriving at 10am rather than waiting to depart from home later site staff might possibly agree, in this case I am doubtful but they can but ask.

Very different. I used to occasionally do as you did. So I would pay for the full Sunday stay as an example and leave at 8pm after 8 hours usage of the site. In this case the OP will arrive on site wit his Sunday booking cancelled as he did not take it up and in any event could not pay for it in advance. ON the CMC forum he was saying that he intended to arrive at 10am. He would not be seen as other than an early arrival. I gave him a suggestion in his first response on CMC forum.: 'I can only suggest that you Talk to the site staff. W&M. I would have thought they would wish you to arrive no earlier than the earliest site arrival time'. I repeat it here lest he missed it.
Much my view

Which insurance - presumably caravan. I can't think why it would affect insurance. I have never given MPTLM values to an insurance company and never been asked about MPTLM and as it is within the caravan design approval I can see no problem personally